Recently, as portable smart devices, such as a smart phone or a tablet PC, are widely supplied, various applications utilized in the smart device are released.
Particularly, there are many cases where the smart devices are commonly mounted with touch screens, so that many applications providing interfaces based on a touch input of a user have appeared.
An operation performed by recognizing a touch input of a user in the smart device mounted with the touch screen includes a function of tracing a trace of a movement of a touch input of a user to enable a screen to be scrolled, a function of enlarging or contracting a screen based on a multi-touch input, or the like.
In general, a touch screen device is designed so as to execute a control function according to a corresponding touch input by applying, by a user, a touch input onto a touch screen by using a finger.
However, according to a characteristic of the touch screen, when the user applies a touch input by using the finger, a palm of the user may be in contact with the touch screen, and in this case, the contact by the palm of the user is recognized as a predetermined touch input, so that the touch screen device is erroneously operated in many cases.
In order to prevent an erroneous operation of the touch screen device by the unintended touch input by the palm and the like, a glove for suppressing the generation of static electricity on the palm is released or touch processing technologies which do not process a touch input generated over a wide range on the touch screen as a normal touch input are introduced, but there is a limit in completely preventing the erroneous operation.
Accordingly, when a user desires to input a predetermined free line onto an electronic document and the like displayed through the touch screen device by using a stylus pen or a finger, erroneous free lines may be input by an unintended touch input, such as a touch by a palm, thereby causing inconvenience to the user.
Accordingly, research on a technology for a touch screen device enabling a selective input of a free line, which supports free lines by an unintended touch input not to be input onto the touch screen when the user draws the free line by applying a touch input onto the touch screen is needed.